1. Field of the Invention
The present invention relates to a seatbelt retractor for use in a seatbelt system for restraining an occupant to protect him in an emergency of a vehicle.
2. Description of the Prior Art
For the webbing retractors, such an arrangement has been commonly used that the remaining portion of the webbing for restraining the occupant is wound up to the take-up shaft biased by a force, made it possible to be freely wound out in the normal running condition of the vehicle, and, in an emergency, a lock bar is engaged with a ratchet wheel solidly secured to the take-up shaft, whereby the wind-out of the webbing is instantaneously stopped, thus reliably securing the occupant.
However, with such a webbing retractor, in an emergency of the vehicle, the tooth top of a lock bar oscillated in an emergency of the vehicle impinges on the tooth top of the ratchet wheel and the lock bar is sprung back, and it takes a long period of time for the lock bar to be reliably engaged with the ratchet wheel to stop wind-out rotation of the ratchet wheel and the takeup shaft, during which time the webbing is wound out to an appreciable extent, whereby the occupant becomes restrained incompletely, thus incurring such possibilities that the function of securing safety of the occupant is impaired.
In view of the above, the applicant, in U.S. patent application Ser. No. 939,421, has proposed a webbing retractor wherein a balancer actuated by an acceleration detector is engaged with the ratchet wheel, whereby the tooth top of the lock bar is reliably engaged with the tooth top of the ratchet wheel without impinging on the tooth top of the ratchet wheel, to thereby stop the wind-out of the webbing for restraining the occupant. However, in this webbing retractor, the balancer is unstable, and there has been such possibilities that, the balancer is oscillated before being engaged with the ratchet wheel when the balancer is actuated by the acceleration detector, or the balancer moves in the axial direction of the ratchet wheel when being engaged with the ratchet wheel, so that the engagement becomes incomplete.